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Abstract:

A weather based irrigation controller has a thermometer that provides a
temperature signal to the controller and a rain gauge that provides a
rainfall signal to the controller, for adjusting irrigation schedules. A
default mode is initiated when either sensor fails, and introduces an
adjustment to the maximum irrigation duration based on historical stored
data.

Claims:

1. A controller for controlling an irrigation schedule in an irrigation
system, the irrigation system including a plurality of sprinkler heads
connected via a plurality of conduits to a water source, the controller
comprising: a rain gauge configured to transmit to the controller a
signal representing a recent rainfall amount; a thermometer configured to
transmit to the controller a signal representing a prevailing temperature
value; an input means for permitting a user to enter irrigation
parameters into the controller, wherein the parameters include: a Maximum
Irrigation Duration; an identifier for identifying the sector in which
the irrigation system is located; the current date; a database that
includes stored information relating to historical meteorological
conditions associated with each of a plurality of sectors located within
a geographical area, the information including, for each sector: the
historical period-average evapotranspiration rate for a plurality of
periods over the duration of a year, the historical average solar
radiation level for each month over the duration of a year; the solar
radiation for the month of average summer high temperature; the average
summer high temperature; wherein, the microprocessor is configured to
calculate and apply an amount of time to suspend the next irrigation
event due to rainfall, the amount of time being based on measured inches
of rainfall divided by the historical period-average evapotranspiration
rate for the current period; further wherein the microprocessor is
configured to calculate and apply a Next Irrigation Duration being equal
to the Maximum Irrigation Duration multiplied by a ratio based on the
product of the historical average solar radiation level for the current
month and the previous day's measured high temperature, divided by the
product of the solar radiation for the month of average summer high
temperature and the average summer high temperature; and wherein the
microprocessor is configured to respond to a failure in receipt of the
signal from at least one of the sensors by calculating and applying an
Actual Irrigation Duration rather than a Next Irrigation Duration, the
Actual Irrigation Duration being equal to the Maximum Irrigation Duration
multiplied by a ratio based on the historical period-average
evapotranspiration rate for the current period divided by the maximum
period-average evapotranspiration rate that occurs in the course of a
year.

3. The controller of claim 1, wherein the sector identifier is a zip
code.

4. The controller of claim 1, wherein the at least one of the sensors is
the thermometer.

5. The controller of claim 1, wherein the at least one of the sensors is
the rain gauge.

6. The controller of claim 1, wherein the microprocessor is configured to
sequentially recalculate the Actual Irrigation Duration in each new
period by applying the historical period-average evapotranspiration rate
associated with each new period, and causing the irrigation system to
irrigate for the Actual Irrigation Duration during the new current
period.

7. The controller of claim 1, wherein the period associated with the
Period Reduction Factor is a month.

8. The controller of claim 1, wherein the period associated with the
Period Reduction Factor is a week.

9. The controller of claim 1, wherein the period associated with the
Period Reduction Factor is a day.

10. A method of controlling an irrigation schedule by an irrigation
system that includes a plurality of sprinkler heads connected via a
plurality of conduits to a water source, the method comprising: compiling
a database that includes information relating to historical
evapo-transpiration rates for a plurality of sectors located within a
geographical area; deriving, from the information, Period Reduction
Factors applicable over a year for each sector, wherein the Period
Reduction Factors are based on the historical period-average
evapotranspiration rate for each period of the year for a sector, divided
by the maximum period-average evapotranspiration rate that occurs in a
year for that sector, whereby the database has an array of information in
which each sector in a geographical area has, associated with it, a
plurality of Period Reduction Factors, one Period Reduction Factor for
each period of the year; entering irrigation parameters into the
controller, wherein the parameters include: a Maximum Irrigation
Duration; an identifier for identifying the sector in which the
irrigation system is situated; and the current date; transmitting from a
thermometer to the controller a signal reflecting a prevailing
temperature value; checking whether the signal is received by the
controller; if the signal is received by the controller, then:
multiplying the Maximum Irrigation Duration by a temperature ratio,
thereby computing a Next Irrigation Duration, wherein the temperature
ratio is based on the product of the historical average solar radiation
level for the current month and the previous day's high temperature,
divided by the product of the solar radiation for the month of average
summer high temperature and the average summer high temperature; causing
the irrigation system to irrigate for the Next Irrigation Duration at the
next irrigation operation; if the signal is not received by the
controller, then: adjusting the Maximum Irrigation Duration by
multiplying the Maximum Irrigation Duration by a Period Reduction Factor
for the current period associated with the sector that has been
identified by the user, thereby obtaining an Actual Irrigation Duration
for the current period for the identified sector; and causing the
irrigation system to irrigate for the Actual Irrigation Duration during
the current period.

11. The method of claim 10, further including: transmitting from a rain
gauge to the controller a signal reflecting an amount of rain that has
fallen; calculating, at historically prevailing rates of
evapotranspiration, an amount of time required for the amount of rainfall
to evaporate; suspending irrigation operations for at least the amount of
time.

12. The method of claim 10, wherein entering a sector identifier into the
controller includes entering a zip code.

13. The method of claim 10 wherein the period associated with the Period
Reduction Factor is one month.

14. The method of claim 10 wherein the period associated with the Period
Reduction Factor is one week.

15. The method of claim 10, wherein the period associated with the Period
Reduction Factor is one day.

16. The method of claim 10, wherein adjusting the Maximum Irrigation
Duration includes sequentially recalculating the Actual Irrigation
Duration in each new period by applying the historical period-average
evapotranspiration rate associated with each new period, and causing the
irrigation system to irrigate for the Actual Irrigation Duration during
the new current period.

17. A method of controlling an irrigation schedule by an irrigation
system that includes a plurality of sprinkler heads connected via a
plurality of conduits to a water source, the method comprising: compiling
a database that includes information relating to historical
evapo-transpiration rates for a plurality of sectors located within a
geographical area; deriving, from the information, Period Reduction
Factors applicable over a year for each sector, wherein the Period
Reduction Factors are based on the historical period-average
evapotranspiration rate for each period of the year for a sector, divided
by the maximum period-average evapotranspiration rate that occurs in a
year for that sector, whereby the database has an array of information in
which each sector in a geographical area has, associated with it, a
plurality of Period Reduction Factors, one Period Reduction Factor for
each period of the year; entering irrigation parameters into the
controller, wherein the parameters include: a Maximum Irrigation
Duration; an identifier for identifying the sector in which the
irrigation system is situated; and the current date; transmitting from a
rain gauge to the controller a signal reflecting an amount of rain that
has fallen; checking whether the signal is received by the controller; if
the signal is received by the controller, then: calculating and applying
an amount of time to suspend the next irrigation event due to rainfall,
the amount of time being based on measured inches of rainfall divided by
the historical period-average evapotranspiration rate for the current
period; causing the irrigation system to suspend the next irrigation
event for the amount of time; if the signal is not received by the
controller, then: adjusting the Maximum Irrigation Duration by
multiplying the Maximum Irrigation Duration by a Period Reduction Factor
for the current period associated with the sector that has been
identified by the user, thereby obtaining an Actual Irrigation Duration
for the current period for the identified sector; and causing the
irrigation system to irrigate for the Actual Irrigation Duration during
the current period.

18. The method of claim 17, wherein entering a sector identifier into the
controller includes entering a zip code.

19. The method of claim 17 wherein the period associated with the Period
Reduction Factor is one month.

20. The method of claim 17 wherein the period associated with the Period
Reduction Factor is one week.

21. The method of claim 17, wherein the period associated with the Period
Reduction Factor is one day.

22. The method of claim 17, wherein adjusting the Maximum Irrigation
Duration includes sequentially recalculating the Actual Irrigation
Duration in each new period by applying the historical period-average
evapotranspiration rate associated with each new period, and causing the
irrigation system to irrigate for the Actual Irrigation Duration during
the new current period.

Description:

BACKGROUND

[0001] The present invention relates to a system and method for regulating
the operation of an irrigation system. More particularly, the invention
pertains to a system and method for regulating the operation of an
irrigation system which is responsive to user programmed information.

[0002] Automatic irrigation systems such as those employed for landscape
and agricultural watering are well known in the art. Typical irrigation
systems use a means of controlling watering cycles via an automatic
controller. The need to control watering cycles due to seasonally
changing environmental conditions is important for saving water, saving
costs, optimizing growing conditions, and preventing unsafe conditions.

[0003] Typically, a user will enter instructions into a microprocessor
based controller that will cause the irrigation system to start
irrigation at a certain time, on certain days, for a certain duration,
according to the user's instructions. Irrigation may be based on "zones"
in which a group of sprinkler heads discharge in unison, or sequentially,
or a combination of both.

[0004] Typically, a user who programs the microprocessor in the summer
month of July to deliver an irrigation event of a certain duration on
certain days from a particular irrigation system, would, if reminded to
attend to the issue, reduce that duration over the fall, winter, and
spring months to take account of changing seasonal environmental
conditions that can be expected to prevail in the vicinity of the
irrigation system, and the user might reduce the duration accordingly
each month, or shorter period, before increasing it again. Frequently,
however, many users tend to forget to downwardly adjust the irrigation
duration after the hot summer months to account for the reduced
evapo-transpiration rates over the following months. At best, a user may
remember to adjust irrigation for some months or a shorter period, but
not others. As a result, the irrigation system may continue to discharge
water in irrigation during the fall and winter at a rate that was
selected to be suitable during the summer, or some other time. This can
be very wasteful, not to mention destructive in the case of certain
crops, grasses, flowers, and shrubs that react adversely to over or under
watering.

[0005] Consequently, solutions have been developed for taking into account
actual prevailing environmental conditions, and for automatically
adjusting irrigation duration to take account of changed conditions in
real time. These solutions typically employ one or more sensors that
monitor changes in environmental conditions in real time. (As used
herein, the term "real time data" refers to information that is acquired
for immediate use, and is distinguished from "historical data" which
refers to data collected on one date in one year for use on a similar
date in a later year. Average historic data is data from a plurality of
previous years that has been averaged to provide one mean value.) A
sensor may be located near an associated controller, and may be linked to
the controller either by wireless communication or by physical
connection. Such a sensor may measure actual precipitation, actual
temperatures, actual wind speed, soil moisture, humidity, and other
environmental factors, all in real time. Based on these measurements
which are transmitted back to the controller, the controller uses
preprogrammed logical algorithms to decide how to adjust a preprogrammed
irrigation schedule to account for changed environmental conditions. For
example, if high temperatures and dry conditions are recorded, irrigation
duration may be increased. If wet or cold conditions are noted,
irrigation may be reduced or suspended altogether.

[0006] However, such weather sensor based systems may have drawbacks and
disadvantages. Typically, weather sensors are mounted where they are
exposed to the elements and once mounted may malfunction, or may be
difficult to maintain in operation. Thus, while a failed sensor is
awaiting repair, the controller may be obliged to discharge an amount of
irrigation water that is not adjusted for prevailing weather conditions,
and that may therefore be wasteful and/or destructive.

[0007] Accordingly, there is a need in the art for a weather based
irrigation controller that may be sold and used universally, that is easy
to use, that is inexpensive to manufacture, that is easy to install,
initialize, maintain, and operate, but that also takes account of the
fact that weather sensors may fail after installation in that it does not
surrender all ability to adjust for seasonal weather variation in the
event of such failure. The present invention addresses these and other
needs.

SUMMARY OF THE INVENTION

[0008] In a preferred embodiment, the invention is a controller for
controlling an irrigation schedule in an irrigation system, the
irrigation system including a plurality of sprinkler heads connected via
a plurality of conduits to a water source. The controller comprises a
rain gauge configured to transmit to the controller a signal representing
a recent rainfall amount. It further includes a thermometer configured to
transmit to the controller a signal representing a prevailing temperature
value. And it further includes an input means for permitting a user to
enter irrigation parameters into the controller, wherein the parameters
include a Maximum Irrigation Duration, an identifier for identifying the
sector in which the irrigation system is located, and, the current date.
It includes a database that includes stored information relating to
historical meteorological conditions associated with each of a plurality
of sectors located within a geographical area, the information may
include, for each sector, (a) the historical period-average
evapotranspiration rate for a plurality of periods over the duration of a
year (b) the historical average solar radiation level for each month over
the duration of a year (c) the solar radiation for the month of average
summer high temperature and (d) the average summer high temperature. In a
preferred aspect, the microprocessor may be configured to calculate and
apply an amount of time to suspend the next irrigation event due to
rainfall, the amount of time being based on measured inches of rainfall
divided by the historical period-average evapotranspiration rate for the
current period. In yet a further aspect, the microprocessor may be
configured to calculate and apply a Next Irrigation Duration being equal
to the Maximum Irrigation Duration multiplied by a ratio based on the
product of the historical average solar radiation level for the current
month and the previous day's measured high temperature, divided by the
product of the solar radiation for the month of average summer high
temperature and the average summer high temperature. And in yet a further
aspect, the microprocessor may be configured to respond to a failure in
receipt of the signal from at least one of the sensors by calculating and
applying an Actual Irrigation Duration rather than a Next Irrigation
Duration, the Actual Irrigation Duration being equal to the Maximum
Irrigation Duration multiplied by a ratio based on the historical
period-average evapotranspiration rate for the current period divided by
the maximum period-average evapotranspiration rate that occurs in the
course of a year. Preferably, the sector identifier is a zip code.
Further preferably, the at least one of the sensors is the thermometer,
but it may also be the rain gauge.

[0009] In another facet, the invention is a method of controlling an
irrigation schedule by an irrigation system that includes a plurality of
sprinkler heads connected via a plurality of conduits to a water source.
The method comprises compiling a database that includes information
relating to historical evapo-transpiration rates for a plurality of
sectors located within a geographical area. Further, the method includes
deriving, from the information, Period Reduction Factors applicable over
a year for each sector, wherein the Period Reduction Factors are based on
the historical period-average evapotranspiration rate for each period of
the year for a sector, divided by the maximum period-average
evapotranspiration rate that occurs in a year for that sector. As a
result of these steps, the database may have an array of information in
which each sector in a geographical area has, associated with it, a
plurality of Period Reduction Factors, one Period Reduction Factor for
each period of the year. The method further includes entering irrigation
parameters into the controller, wherein the parameters include a Maximum
Irrigation Duration, an identifier for identifying the sector in which
the irrigation system is situated, and the current date. Further steps
may include transmitting from a thermometer to the controller a signal
reflecting a prevailing temperature value, and checking whether the
signal is received by the controller. If the signal is received by the
controller, then, the step of multiplying the Maximum Irrigation Duration
by a temperature ratio, thereby computing a Next Irrigation Duration,
wherein the temperature ratio is based on the product of the historical
average solar radiation level for the current month and the previous
day's high temperature, divided by the product of the solar radiation for
the month of average summer high temperature and the average summer high
temperature, and causing the irrigation system to irrigate for the Next
Irrigation Duration at the next irrigation operation. However, if the
signal is not received by the controller, then the step of adjusting the
Maximum Irrigation Duration by multiplying the Maximum Irrigation
Duration by a Period Reduction Factor for the current period associated
with the sector that has been identified by the user, thereby obtaining
an Actual Irrigation Duration for the current period for the identified
sector; and causing the irrigation system to irrigate for the Actual
Irrigation Duration during the current period. In a further aspect, the
invention may include transmitting from a rain gauge to the controller a
signal reflecting an amount of rain that has fallen, followed by
calculating, at historically prevailing rates of evapotranspiration, an
amount of time required for the amount of rainfall to evaporate, and
suspending irrigation operations for at least the amount of time.

[0010] In yet a further facet of the invention, the invention is a method
of controlling an irrigation schedule by an irrigation system that
includes a plurality of sprinkler heads connected via a plurality of
conduits to a water source. In this facet, the method comprises compiling
a database that includes information relating to historical
evapo-transpiration rates for a plurality of sectors located within a
geographical area; deriving, from the information, Period Reduction
Factors applicable over a year for each sector, wherein the Period
Reduction Factors are based on the historical period-average
evapotranspiration rate for each period of the year for a sector, divided
by the maximum period-average evapotranspiration rate that occurs in a
year for that sector, whereby the database has an array of information in
which each sector in a geographical area has, associated with it, a
plurality of Period Reduction Factors, one Period Reduction Factor for
each period of the year. The method includes entering irrigation
parameters into the controller, wherein the parameters include a Maximum
Irrigation Duration, an identifier for identifying the sector in which
the irrigation system is situated, and the current date. In a preferred
aspect, the method includes transmitting from a rain gauge to the
controller a signal reflecting an amount of rain that has fallen,
checking whether the signal is received by the controller and, if the
signal is received by the controller, then calculating and applying an
amount of time to suspend the next irrigation event due to rainfall, the
amount of time being based on measured inches of rainfall divided by the
historical period-average evapotranspiration rate for the current period.
The irrigation system is caused to be suspend the next irrigation event
for the amount of time. On the other hand, if the signal is not received
by the controller, then, the step of adjusting the Maximum Irrigation
Duration by multiplying the Maximum Irrigation Duration by a Period
Reduction Factor for the current period associated with the sector that
has been identified by the user, thereby obtaining an Actual Irrigation
Duration for the current period for the identified sector; and causing
the irrigation system to irrigate for the Actual Irrigation Duration
during the current period.

[0011] These and other advantages of the invention will become more
apparent from the following detailed description thereof and the
accompanying exemplary drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

[0012] FIG. 1 is a schematic view of an irrigation system having features
of the present invention.

[0013] FIG. 2 is a schematic view of an irrigation controller as
exemplified in FIG. 1.

[0014] FIG. 3 is a graph of average evapo-transpiration rates in five
different geographical sectors in California, over the period of one
year.

[0015] FIG. 4. is a graph of Monthly Period Reduction Factors for the
sector Fresno, Calif.

[0016] FIG. 5 is a flow diagram showing steps taken in a preferred
embodiment of the invention.

[0017]FIG. 6 is a flow diagram showing steps taken in a preferred
embodiment of the invention.

[0018] FIG. 7 is a flow diagram showing steps taken in another preferred
embodiment of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0019] With reference to the drawings, which are provided for
exemplification and not limitation, a preferred embodiment of an
irrigation controller is described having features of the present
invention.

[0020] With respect to FIG. 1, a typical irrigation system 20 includes a
plurality of sprinkler heads 22, all linked by conduits 24 to a source 26
of water pressure, the heads being configured to discharge water onto a
surrounding landscape either in unison, or one after the other, or in a
combination of both. This system may include a number of "zones," in
which sprinkler heads are dedicated to act in unison in different parts
of a landscape. The overall system may be controlled by a single
electronic controller 28, which activates water to flow in different
portions of the system 20 at different times, and for selected durations.

[0021] In this context, a preferred embodiment of the present invention is
described with respect to the figures. A preferred embodiment provides an
irrigation system 20 that automatically adjusts the amount of water to be
discharged by the system onto a surrounding landscape, according to
anticipated environmental conditions in the vicinity of the system. A
sprinkler controller 28 is provided that harnesses a microprocessor 30.
(FIG. 2, showing the microprocessor schematically within the controller.)
The controller also includes input means 32 such as a toggle switch for
entering parameters such as the present time and date, the times of day
to commence irrigation in each zone, the duration for an irrigation
event, and the like into the microprocessor. It also includes an LCD
screen 33 to facilitate entry of parameters. The controller 28 is
operatively connected with conduits 24 that lead water from a supply 26
to a plurality of sprinkler heads 22 forming part of the irrigation
system 20. The microprocessor 30 is configured to interpret instruction
data that has been input by a user, and consequently to initiate
irrigation via the conduits 24 according to such data, most particularly
to commence irrigation and then to terminate irrigation after an
appropriate irrigation duration has been completed. Such irrigation
initiation is achieved through switched valves 27 that are electrically
operated and are interposed between the controller 28 and the water
supply 26, and operatively connected to the controller 28 via electrical
wires 23.

[0022] Additionally, as seen in FIGS. 1 and 2, the controller may be in
operative communication with a thermometer 100 and also in operative
communication with a rain gauge 102. Communication may be by wireless
communication, or it may be by wired connection. The thermometer may be
of known design and construction, capable of transmitting a signal
representing the prevailing temperature level. The rain gauge may be of
known design and construction, preferably of tipping bucket design such
as described in U.S. Pat. No. 3,943,762, which is incorporated herein by
reference, and capable of transmitting a signal representative of an
amount of rain that has fallen.

[0023] In a first aspect, the irrigation system of the present invention
is configured to operate in a number of different "modes" that may be
applied simultaneously, or sequentially, as described herein. In summary,
there are at least two modes of operation, including a "weather station
mode," and a "historical mode."

[0024] The weather station mode includes reliance upon two real time
weather sensors, namely, the thermometer and the rain gauge referenced
above. These sensors provide information that permits the irrigation
controller to adjust a user pre-programmed irrigation schedule according
to actual prevailing weather conditions. Thus, the weather station mode
is divided into sub-modes that include a "weather station mode
(temperature)" and a "weather station mode (rain)." As will be more fully
explained below, the weather station mode (temperature) uses the
thermometer to measure the daily temperature. The temperature level is
transmitted to the processor by electronic signal. An algorithm in the
processor then causes the controller to adjust the irrigation duration to
prevent under-watering or over-watering depending on the previous day's
maximum temperature. The weather station mode (rain), on the other hand,
uses the rain gauge to measure any rainfall. The amount of rainfall is
transmitted to the processor by electronic signal. An algorithm in the
processor then causes the controller to suspend all irrigation for a
period calculated to prevent duplication by irrigation of the watering
that has taken place through rainfall.

[0025] However, the invention is also configured to take into account the
fact that sensors are delicate components that may periodically fail, and
that a significant amount of time may elapse before a failed sensor is
detected and/or repaired. To take account of such possible failure, the
invention includes a "historical mode" that provides an irrigation
adjustment mode to substitute for a failed receipt of sensor signal. If
the thermometer fails, alternatively, in another embodiment, if either
the thermometer or the rain gauge fails, the historical mode will be
activated and will provide a basis for irrigation adjustment based on
historic data stored in the controller during manufacture, and prior to
the sale of the controller to the end user. Thus, the invention includes
two possible embodiments. In a first embodiment (exemplified with
reference to FIG. 6), two separate electrical signals carry the signal
for each sensor. In this first embodiment, failure of the thermometer
signal alone will trigger the historical mode and terminate the weather
station mode (temperature), while the weather station mode (rain) will
continue simultaneously with the historical mode for as long as the rain
sensor signal continues. Under this first embodiment, if the rain gauge
signal alone fails, the historical mode will not be triggered because the
integrity of each one of the two signals is measured independently of the
other. In a second embodiment (exemplified with reference to FIG. 7), a
single electrical impulse may carry the signal of both the thermometer
and the rain gauge together to the controller. In this second embodiment,
failure of either the rain or the temperature signal will trigger the
historical mode because the electrical pulse as a whole will register
with the microprocessor as corrupted.

[0026] The sequence and conditions under which the different modes of the
irrigation controller may be initiated may be understood more fully with
reference to FIGS. 6 and 7. This sequencing aspect of the invention will
first be described. Thereafter, the features of the different modes
themselves will be fully described. As seen with reference to the
figures, the irrigation controller is first initialized 302 by the user
who manually enters information to populate the required data fields of
the processor. Such data may include irrigation operation start times,
irrigation durations, the geographical zip code of the location of the
controller, the current date, data relating to the rain gauge (preferably
based on a tipping bucket configuration) and data relating to the
thermometer. Once the controller is initialized, it will automatically
initiate 304 the weather station mode. The weather station mode initiates
the rain 306 sub-mode and the temperature 320 sub-mode to operate
simultaneously.

[0027] Under the first embodiment (exemplified in FIG. 6), a subroutine of
the processor checks 308 the status of the signal from the rain gauge and
the signal from the thermometer. If the rain signal fails while the
temperature signal is still operational, then the controller terminates
310 any irrigation adjustment based on rainfall, while allowing
adjustment based on the temperature to continue. Thus, in these
circumstances, only temperature based adjustment is applied.

[0028] Continuing to describe operation of the controller under the first
embodiment, if the temperature signal fails 322 at any time, then the
controller initiates 324 the historic mode. As explained more fully
herein below, the historic mode relies upon a database that correlates
the time of year, specifically, the date, with an average
evapotranspiration rate applicable in the relevant geographical sector on
that date to make irrigation adjustments. Once initiated, the historic
mode continues to operate 326 until such time as the thermometer signal
is repaired.

[0029] Thus, if the processor check 312 reveals that the rain signal fails
after the thermometer signal has failed and the historic mode has
therefore been initiated, the controller will terminate 314 the rainfall
mode and will allow the controller to operate only in historic mode.
However, if the temperature mode fails while the rainfall mode continues
to operate, the controller may operate under both historic mode and
rainfall mode.

[0030] These sequences allow the controller to advantageously initially
apply irrigation adjustments based on prevailing rain and temperature
conditions while both weather sensors are operating. However, if the
temperature sensor fails, the controller is configured to make an
adjustment based on an estimate of temperature effects, where the
estimate is derived from stored historical evapotranspiration values. If
only the temperature sensor has failed, the rainfall based irrigation
adjustments continue. However, if the rainfall sensor fails, the
controller may ignore the duplicative effect of rain and makes no
irrigation adjustment therefor, but continues to make adjustments based
on temperature values, or on historical evapotranspiration values should
they be applicable. This aspect of the invention provides an advantageous
improvement over the prior art because it ameliorates the problem that
may arise in the event the delicate electronic equipment employed in the
present invention should gradually fail, as may occur in a robust outside
environment like that in which the present art is intended to operate.
Instead of the irrigation adjustment component of the controller becoming
entirely disabled during the period that the failures are not repaired, a
backup system provides reasonable estimates of the effects of
temperature, based on historical records, of what adjustments would be
called for in the absence of any failure.

[0031] By contrast, under the principles of operation of the second
embodiment (exemplified in FIG. 7) in which the signals of the rain gauge
and the thermometer are combined into a single electronic pulse, failure
of either signal may corrupt the entire pulse. Thus, upon the failure in
the signal of either the rain gauge sensor or the temperature sensor,
that is, upon detection of corruption in the single pulse, the processor
is configured to terminate both the rain sub-mode and the temperature
sub-mode, and initiate the historic mode 400.

[0032] When the user purchases and installs an irrigation control system
20 having features of the present invention, the controller 28 calls for
certain information via the LCD screen 33, by prompting the user to enter
the information sequentially via the input means 32. (FIG. 2.) In
addition to the usual start times for each irrigation event in each of a
plurality of zones, one important parameter that the user will be
requested to enter in conjunction with each start time is the Maximum
Irrigation Duration ("Dmax") for each irrigation event that the user
wishes to occur during the period that the evapotransipiration rate ("ET
rate") will be greatest in the location where the control system is being
installed. A fuller description of ET rate is provided below. For
example, although the user may be installing and setting up the unit in
March, the controller will ask the user to enter the maximum irrigation
duration (Dmax) that he wishes to apply at the peak of summer when the ET
rate is greatest. Another parameter that the user will be requested to
enter is the current date, and another is the identity of the sector in
which the system 20 is being set up to operate. For a system intended to
operate in the United States, this latter parameter will preferably be
the postal zip code in which the system is installed, although cities or
counties may also be used. The significance of these parameters will be
explained below.

[0033] Weather Station Mode (Temperature)

[0034] As previously noted, in one aspect of the invention, the processor
may apply a Weather Station Mode (Temperature). This mode is preferred
for adjustments made due to prevailing temperature because it narrowly
follows the temperature prevailing at the site of the controller. To
operate under this mode, the controller receives data from the
thermometer that measures the actual daily temperature in the vicinity of
the controller, and notes the daily maximum temperature. This information
is used in an algorithm for irrigation duration adjustment, as described
below.

[0035] To enable this mode, the database in the microprocessor is
configured to include a collection of stored data for geographic sectors
that, preferably, may be conveniently identified by postal zip code (or
other sector identifier such as city or county). This data is entered
into the database by the manufacturer before the controller is sold. When
the user enters into the controller the geographic zip code of the sector
in which the controller is intended to be used, the microprocessor
effectively knows where the controller is geographically located, based
on the zip code. In each data set related to each sector, preferably by
zip code, there is stored the following information: (i) The historic
average summer high temperature; (ii) The historic average solar
radiation level for the month in which the average summer high
temperature occurred; and (iii) The historic average solar radiation
level for each of the twelve months of the year, so that the historic
average solar radiation level for the current month may be extracted
based on the current date.

[0036] Using the above information, and using the previous day's high
temperature (as measured by the thermometer), the microprocessor in the
controller is configured to daily calculate a "temperature ratio" which
is used to adjust irrigation durations for each sector, each day, as
follows: (a) Identifying the historical average solar radiation level for
the current month (A) from the database; (b) Identifying the previous
day's high temperature, as measured by the thermometer (B); (c)
Identifying the solar radiation for the month of average summer high (C)
from the database; (d) Identifying the average summer high temp (D) from
the database: (e) Determining the product of A and B divided by the
product of C and D, or (A×B)/(C×D), as being the "temperature
ratio."

[0037] This "temperature ratio" is applied as a reduction factor against
the user designated irrigation runtime for the summer high month, or the
Maximum Irrigation Duration (Dmax) as previously described herein. The
resulting duration arising from the product of the temperature ratio and
the Maximum Irrigation Duration is referred to herein as the Next
Irrigation Duration. It may be noted that the Next Irrigation Duration is
preferably calculated daily before the day's irrigation occurs, based on
the previous day's high temperature. As a result, the Next Irrigation
Duration on one day is likely to differ from that of the previous day.

[0039] The historical mode is a mode that the controller is configured to
apply in the event that the thermometer signal fails (under the first
embodiment, FIG. 6), or alternatively, where either the thermometer or
rain gauge signal fails (under the second embodiment, FIG. 7). In an
important aspect of this historical mode, the microprocessor 30 includes
a database 34 configured to enable the controller 28, independently of
the user and independently of any real time temperature measurements, to
adjust the duration of irrigation for an irrigation event that has been
instructed by the user. This adjustment is directed at reducing the
amount of water discharged during irrigation for periods of the year when
the evapo-transpiration ("ET") rate in the vicinity of the system 20 is
lower than at its peak level. The peak level typically occurs some time
in June through August of any year in the northern hemisphere.
Evapo-transpiration is a term used to describe the sum of evaporation and
plant transpiration from the earth's land surface to atmosphere.
Evaporation accounts for the movement of water to the air from sources
such as the soil, canopy interception, and waterbodies. Transpiration
accounts for the movement of water within a plant and the subsequent loss
of water as vapor through stomata in its leaves. Evapo-transpiration is
an important part of the water cycle. Historical records of the ET rate
for the United States have been kept and are available from a number of
sources, including government managed weather stations such as CIMIS
(California Irrigation Management Information System, maintained by the
California Department of Water Resources), CoAgMet maintained by Colorado
State University-Atmospheric Sciences, AZMET maintained by University of
Arizona-Soils, Water and Environmental Science Department, New Mexico
State University-Agronomy and Horticulture, and Texas A&M
University-Agricultural Engineering Department. Although slight
variations in the methods used to determine the ET values do exist, most
ET calculations are based on the following environmental factors:
temperature, solar radiation, wind speed and humidity. A typical plot of
average evapo-transpiration rates against time for different cities in
California in the United States over the period of a year is shown in
FIG. 3.

[0040] In a preferred aspect of the invention, the database 34 includes
historical records of the ET rate over a year throughout a geographical
area, preferably throughout the United States, and also preferably
throughout any part of the world in which historical ET rate records are
known and where the irrigation system 20 may be used. The geographic area
for which the database 34 is compiled is preferably broken down into a
plurality of smaller sectors, each sector being identified for example by
the name of a nearby town, or by county name, or even by state, where the
ET rates are relatively uniform, but most preferably may be identified by
a postal zip code as a small area within which the ET rates are likely to
be uniform. Thus, in a preferred embodiment, the database 34 is compiled
to reflect the historical average ET rate in each postal zip code area in
the United States for a monthly, weekly, or shorter time period, over the
duration of a year. While a month is a useful period of time in which to
capture the changes in ET rate in a sector, a half-monthly period
provides a smoother transition over the course of a year, and a weekly or
daily period provides an even smoother transition. Daily average ET rates
are also available in the historical record, and these rates may be used
where it is desirable to follow a precise transition over the course of a
year in short increments. For example, in FIG. 3, the ET rates for
different parts of California are shown on curves that are smoothed and
from which daily ET rates can be extracted. Similar records are available
throughout the United States and other countries.

[0041] It will be understood that in a country such as the United States,
many zip codes that are relatively closely situated will share the same
ET data over the course of a year, but this fact need does not alter the
ease with which each zip code may be assigned the appropriate ET data
from historical sources. To this end, although the controller 28 may call
for the entire zip code to be entered by a user, the database may be
based on only the first three digits of a zip code, thus giving a less
detailed breakdown of ET rates, although no less effective.

[0042] Once the above described data is assembled for a geographical area,
it is processed by performing 202 (FIG. 5) the following steps for each
sector (e.g., zip code): (a) Identifying the maximum period-average ET
rate that occurs in a year, "ETmax" (typically occurring some time June
through August in the northern hemisphere); (b) Identifying the
historical period-average ET rate for each period of the year,
"ETperiod."; (c) Dividing ETperiod by ETmax, to provide a Period
Reduction Factor for each period of the year, the "PRF" for each period.

[0043] As used above, the term "period" may refer to the period of a
month, although a half-monthly, weekly, or even daily period may apply
where appropriate.

[0044] Thus, preferably before a user even purchases a controller of the
present invention, and therefore before any instructions have been
entered into the microprocessor 30 by the user, the manufacture has
compiled and stored 204 (FIG. 5) in the database 34 an array of
historical information in which each sector (preferably, zip code) in a
geographical area has, associated with it, a plurality of PRFs--one for
each period of the year whether the period be a month, a half-month, a
week, or a day. (See, FIG. 4.) It will be appreciated that alternative
methodologies may be used to assemble the database 34. For example, the
ET rates themselves may be entered into the database, in which an
algorithm may be selected to extract the relevant PRF for application,
but eventually an applicable PRF is derived from data within the
microprocessor and all such methodologies are contemplated as falling
within the scope of the invention.

[0045] Once the duration Dmax, the current date, and sector identification
are entered 206 (FIG. 5), the microprocessor 30 performs the following
adjustments to take into account the inevitable seasonal changes, and the
changing ET rates, over the duration of a year. Based on the current
date, the microprocessor selects the appropriate PRF for the applicable
sector from the database 34. The microprocessor then computes 208 (FIG.
5) an Actual Irrigation Duration ("Dactual") for the current period by
multiplying the maximum duration, Dmax, entered by the user, by the PRF
for that period obtained from the database 34. Thus, in the period of
January, for example, when the ET rate for a particular sector may be
only 16% of the maximum summer ET rate in that sector (so that the PRF
for January is 16%), the Actual Irrigation Duration, Dactual, will be
computed to be 16% of Dmax. (See FIG. 4). The microprocessor 30 then sets
the applicable duration for current irrigation events to be the Actual
Irrigation Duration, Dactual, and not the maximum irrigation duration,
Dmax. For other or shorter periods, the same principle will apply. Then,
when the time arrives for irrigation on any day, the microprocessor 30
causes 214 (FIG. 5) the irrigation system to irrigate for a period of
time Dactual rather than Dmax. This process is exemplified in FIG. 5.

[0046] Moreover, after the current "period" has passed (as noted, "period
may be month, half month, week, day or other suitable time period), the
microprocessor 30 is configured to sequentially recalculate the Actual
Irrigation Duration in each new period by applying the Period Reduction
Factor (PRF) associated with each new period, and causing the irrigation
system to irrigate for the resulting Actual Irrigation Duration (Dactual)
during the new current period. (See, FIG. 5.) For example, the curves of
ET rate in FIGS. 3 and 4 show smoothed curves from which the Dactual may
be derived on a daily basis.

[0047] It will be appreciated that, in use of the historic mode, after the
above procedure of information entry and duration adjustment has been
completed in a period that does not coincide with maximum ET rate, a user
may monitor the actual irrigation duration, Dactual, caused by the
controller according to the above described process. After observing the
actual irrigation durations, it is possible that a user may conclude that
insufficient water (or too much water) is being caused to discharge by
the controller in each irrigation event. Under these circumstances, a
user may manually alter the Dmax that he had previously input, so that
the current Dactual increases or reduces proportionally. When the user is
satisfied that the Dactual for the current period is acceptable, he can
reasonably assume that the Dactual that will be caused in the period of
greatest ET rate (that will in effect be 100% of Dmax) will be
appropriate for that period also. Thus, by a series of small initial
adjustments, even during a seasonal period when maximum ET rate does not
exist, a user may achieve an optimal rate of irrigation that applies over
the period of a whole year.

[0048] In the manner described, once the data entries have been made and
adjustments are concluded, it will be appreciated that the microprocessor
continually adjusts the irrigation duration for any individual sprinkler
system to take into account the historic variation in period average ET
rates over the period of a year, each adjustment being made incrementally
after a period of time which may be a month, a half month, a week, or a
day, depending on the requirements of the irrigation project. Preferably,
use of the smooth ET rate and PRF curves exemplified in FIGS. 3 and 4
would permit adjustment to be made on a daily period basis.

[0049] This aspect of the invention thus has the advantage of efficiently
and rationally applying a modification in water irrigated onto a
landscape to accommodate the seasonal changes in historical ET rate of a
particular sector, without reference to any temperature measurements in
real time. The invention has versatility in that it may be sold, with a
preprogrammed database 34 that includes either a table of Period
Reduction Factors (PRFs), or the information necessary (e.g. ET rates) to
extract, via an algorithm, PRFs in any sector based, preferably, on the
postal zip code where the system 20 will be used. Thus, a purchaser may
install such a system in Mississippi or in California and enter the
information required to initialize the system, including the zip code
where the system is to be used, and the date. In each case the
information in the database allows the microprocessor 30, by using the
database 34, to periodically select the duration of actual irrigation
(Dactual) for any particular sector in a way that is rationally and
efficiently based on the changing seasonal ET rate in the selected
sector, and accounts for likely rainfall, and for dry, hot, and windy
conditions. This aspect of the invention has the considerable advantage
of relieving the user of responsibility for manually adjusting the
duration for irrigation every period, which a user typically may forget
to do after a few adjustments. It also has the advantage of achieving a
result that is very similar to a result in which a sprinkler system uses
a thermometer to measure the actual temperature as a basis for
adjustment. This is particularly useful in situations where a thermometer
that was once in communication with the controller has failed, leaving
the controller without any real time information about the actual
prevailing temperature conditions.

[0050] It will be appreciated that the Actual Irrigation Duration that is
applied under the historical mode, differs from the Next Irrigation
Duration that is applied based on prevailing temperature. In the case of
the historical mode the Actual Irrigation Duration will be applied
throughout a "period" which may be a month, a week, or a day, depending
on the embodiment of the invention that is affected; whereas the Next
Irrigation Duration depends on the maximum temperature of the previous
day.

[0051] Weather Station Mode (Rain)

[0052] In another aspect of the invention, the processor may apply a
Weather Station Mode (Rain) for adjusting an irrigation schedule
according to prevailing rainfall. Preferably, this mode operates
simultaneously with the Weather Station Mode (temperature). As previously
noted, this mode may be terminated when the rain gauge signal alone fails
if the signals are separately transmitted (first embodiment, FIG. 6), or
when either one of the sensor signal fails if the two signals are
transmitted as one pulse (second embodiment, FIG. 7). In order to operate
in this mode, the controller may be configured to use the same historical
data, stored in the database described above with reference to FIG. 3, to
calculate an amount of time the entire irrigation system should be
suspended from operation, after rain has been detected. In this regard,
the controller is operatively connected to a rain measuring device that
preferably follows a known tipping bucket design. An example of a
suitable tipping bucket is disclosed in U.S. Pat. No. 3,943,762 which is
incorporated herein by reference. The tipping bucket is configured to
measure an accumulated amount of rain that has fallen in a region under
control of the controller. Each time the bucket tips, this fact reflects
that a certain amount of rain has accumulated since the last time it
tipped, and a signal is sent to the controller informing that the bucket
has tipped and therefore that a threshold amount of rain has fallen.
Based on the received signal from the tipping bucket, the processor
applies an algorithm (described in detail below) to determine for how
long all irrigation operations should be suspended in order not to
wastefully duplicate the rainfall with irrigated water.

[0053] In general, to achieve this result, the algorithm relies upon
information in the same stored database which records the average
historical evapotranspiration rate for each sector over each period in a
year, as described above and exemplified in FIG. 3. The data is relied
upon to calculate and determine a "rain evaporation time equivalent,"
which represents the amount of time that would be required to evaporate
the rainfall measured by the tipping bucket, under the average seasonal
historical evapotranspiration rate for the current date. The controller
is configured to suspend the irrigation system for this amount of time.

[0054] The algorithm for irrigation suspension caused by rain operates
under the following principles: As noted, the rain gauge in communication
with the controller will preferably operate as a tipping bucket style
rain gauge, for which each tip of the bucket represents a certain amount
of rain that has recently fallen. In a preferred embodiment, each tip of
a bucket represents 0.0325 inches of fallen rain. After the first tip of
the bucket, the microprocessor identifies in the database a stored value
which is the historical period-average evapotranspiration rate for the
current period, referred to here for convenience as ETcurrent. (This is
the same value used in the historic mode as the numerator of the Period
Reduction Factor, and, as indicated in FIG. 3, its units are preferably
inches of freestanding water evaporated per day.) To obtain the amount of
time, as a fraction of a day, that it will theoretically take for the
measured rainfall to evaporate under the historical period-average
evapotranspiration rate for the current period, the processor divides the
inches of rainfall by the ETcurrent. For example, 0.0325 inches of
rainfall, divided by 0.095 inches evaporation per day for Fresno in April
(see FIG. 3) equals about 0.34 days (or 8.1 hours). The controller is
configured to then suspend the upcoming irrigation event for a period of
8.1 hours. This suspension prevents the controller from causing the same
amount of water from being discharged onto a landscape through irrigation
that has just fallen as rain, and it has a conserving effect on water
supply while at the same time protecting the landscape from possible
damage due to overwatering.

[0055] In yet a further preferred aspect of the invention, the controller
may place limits on the duration of the calculated irrigation suspension.
Under this aspect a limit, or a "cap," is placed on the duration of an
irrigation suspension period in the amount of six hours for the first tip
of a bucket (or, 0.0325 inches of rain). Upon the second tip, the
controller imposes a maximum of 24 hours for the suspension period.
Thereafter, a maximum of 96 hours suspension is placed on any future
suspension computed to be applicable by the microprocessor. By thus
"capping" the period of irrigation suspension, the invention takes
account of the assumption upon which the calculations are based, that
fallen rain is free standing on the ground. In reality, fallen rain may
run off the ground to a drainage system or catchment area, or it may
saturate the soil. Thus, the amount of time that is theoretically
calculated for rain to evaporate when it falls on dry soil may be longer
than the time required in reality for the rainfall to evaporate.
Therefore, the first two bucket tips are considered differently than the
remaining tips, and the suspension periods calculated by the processor
are capped as described for only the first two tips. However, once the
first two tips have occurred and the appropriate suspension periods
imposed, the assumption that the rainfall has become freestanding water
is more realistic because the ground condition will have become more
saturated, and no further caps are applied arising from bucket tips after
the second tip. Finally, in a further aspect of the invention, an overall
cap of 96 hours is preferably placed on any future calculated suspension
period. Under this aspect, if a series of bucket tips are measured, the
maximum amount of future time that irrigation will be suspended is 96
hours regardless of the calculated requirement. This is a safety feature
which guards against possible malfunction of the rain gauge or any aspect
of the invention. It is contemplated that 96 hours (four days) is a
substantial period over which to suspend all irrigation. Accordingly, the
microprocessor is preferably configured to not permit any single period
of irrigation suspension to exceed 96 hours without the intervention of
at least some rain (as measured by the rain gauge) during that time. Thus
if, say, 36 hours of a 96 hour calculated suspension have run their
course to leave a remaining 60 hour suspension requirement, and rain is
again measured in the form of a bucket tip, the additional calculated
suspension is added to the remaining 60 hour suspension subject to the 96
hour upper limit.

[0056] These features have the advantage of providing a structure adapted
to conserve water and preserve crops and vegetation from destruction by
over or under watering during overall irrigation. Thus, it will be
apparent from the foregoing that, while particular forms of the invention
have been illustrated and described, various modifications can be made
without parting from the spirit and scope of the invention.